1. Field of the Invention
The present invention relates to a keyboard device suitable as an input/output device for use in a word processor, personal computer, or the like.
2. Description of the Related Art
FIG. 8 illustrates a keyboard device used as an input/output device. The keyboard device is constructed of various parts in the following manner. Switches are constructed with an insulating substrate 50 on which a conductor (not shown) is formed and a flexible circuit board 51 placed on the insulating substrate 50.
A supporting member 52 is made of a synthetic resin in such a manner so as to include holders 52a each having a circular hole 52b and also includes holders 52c having a rectangular hole 52d, wherein a plurality of sets of holders 52a and 52c are disposed along a plurality of lines. The supporting member 52 is placed on the circuit board 51.
One end of a first operating member 53 is slidably fit into the hole 52d, and one end of a second operating member 54 is pivotably fit into the hole 52b. The first and second operating members 53 and 54 are connected to each other via a shaft 55 so that they cross each other.
A keytop 56 is made of a synthesis resin in such a manner so as to have a supporting member 56a including a circular hole 56b and also have a supporting member 56c including a rectangular hole 56d. The other end of the first operating member 53 is fit into the hole 56b and the other end of the second operating member 54 is fit into the hole 56d so that the keytop 56 is held on the first and second operating members 53 and 54.
A plurality of sets of one keytop 56 and first and second operating members 53 and 54 constructed in the above-described manner are disposed along a plurality of lines. A plurality of dome-shaped elastic members 57 made of electrically insulating rubber are disposed on the circuit board 51 in such a manner that one elastic member 57 is located under each set of first and second operating members 53 and 54.
As described above, each keyswitch is constructed with one pair of first and second operating members 53 and 54, one keytop 56, and one elastic member 57. Although not shown in FIG. 8, a plurality of similar keyswitches are disposed along a plurality of lines.
As shown in FIG. 9, the first and second operating members 53 and 54 are formed in such a manner that the distance Y from the shaft 55 to any end of the operating members is equal.
If the keytop 56 of a certain keyswitch having the above structure is pressed, the ends of the first and second operating members 53 and 54 are, as can be seen from FIG. 8, pressed by the keytop 56. As a result, the first and second operating members 53 and 54 connected to each other via the shaft 55 at their center are moved in such a manner that one end of the first operating member 53 slides in the hole 52d of the supporting member 52c while the other end turns in the hole 56b of the supporting member 56a, and, similarly, one end of the second operating member 54 turns in the hole 52b of the supporting member 52a while the other end slides in the hole 56d of the supporting member 56c. Thus, the keytop 56 moves downward while maintaining itself horizontal.
The elastic member 57 is thus pressed by the first and second operating members 53 and 54, and finally the dome-shaped elastic member 57 is inverted in shape. As a result, the circuit board 51 is pressed by the elastic member 57 and comes in contact with the conductor disposed on the insulating substrate 50. Thus, the switch is turned on.
If the pressing force against the keytop 56 is removed, the first and second operating members 53 and 54 and the keytop 56 are pushed back by the elastic force of the elastic member 57 to their original positions where they were located before being pressed. The pressure by the elastic member 57 against circuit board 51 is released and the circuit board 51 returns to its original position by its own restoring force. As a result, the contact between the circuit board 51 and the conductor on the insulating substrate 50 is released and thus the switch is turned off.
The motion of the keytop 56 during the switching operation will be described in further detail below referring to FIGS. 9 and 10. FIG. 9 illustrates the keytop 56 in the original position before being pressed, and FIG. 10 illustrates the keytop 56 in the pressed position. The keytop 56 is supported by the first and second operating members 53 and 54 wherein the first and second operating members 53 and 54 are formed in such a manner, as described above, that the distance Y from the shaft 55 to any end of the operating members is equal.
Therefore, if the keytop 56 is pressed when it is in the original position as shown in FIG. 8, the keytop 56 moves downward from the original position while maintaining itself horizontal. When the keytop 56 stops at its pressed position as shown in FIG. 10, the keytop 56 is still horizontal as is in the original position.
In general, keyboard devices include a plurality of keyswitches located along a plurality of lines. In operation, an operator puts his/her fingers on keyswitches in a central line, and moves a particular finger onto a desired keyswitch in another line located nearer to or farther from the operator so as to press the keyswitch.
When an operator presses a keyswitch in a line nearer to the operator, the keyswitch is most likely pressed in a direction denoted by an arrow P1 in FIG. 8. On the other hand, when a keyswitch in a line farther from the operator is pressed, it is most likely that the keyswitch is pressed in a direction P2.
As described above, the pressing position on a keytop and the direction in which the keytop is pressed vary depending on whether the keyswitch is located in a near line or a far line. However, in the conventional keyboard device, when a keytop 56 is pressed, it moves downward from its original position to the final pressed position while maintaining itself horizontal, and thus keytop motion occurs in a direction different from the direction in which the keytop is pressed. This can cause stiffness in the operation of the keytop 56. Thus there is a need for an improved keyboard device which can be operated more smoothly.